Rheological and Calorimetric Characterization of the Role of CaCl₂ on Portland Cement Early Hydration

Abstract:

Paper describes a new way how to characterize early hydration and setting of Portland cement pastes with various dosages of setting accelerator CaCl₂. The aim was not to characterize the role of well-known setting accelerator CaCl₂ but to correlate rheology and calorimetry in view of early hydration of Portland cement. Characterization was based on measurements on rotational rheometer, isothermal calorimeter and semiadiabatic calorimeter. The courses of calorimetric exotherms in time were correlated to the development of the phase angle obtained by rheological oscillation tests. Heat flow peaks can be successfully correlated to rheological processes described by change of storage and elastic moduli up to the time that corresponds to the start of the setting which was found to be the limit for rheological tests. The start of the setting on calorimetric curve belongs to the onset point of the main silicate peak during acceleration period of hydration. The value of phase angle decreases as the setting cement paste changes from liquid to solid-like. Times of low values of phase angle ~ 2.5 (°) can be related to times of onset points of main peak for every dosage of setting accelerator.

• Periodical: Materials Science Forum (Volume 865)
• Pages: 17-21
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.865.17
• Online since: August 2016
• Authors: Martin Boháč*, Radoslav Novotný
• Keywords: Early Hydration, Isothermal Calorimetry, Portland Cement, Rheology, Semiadiabatic Calorimetry, Setting

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